Paint shops in general and particularly those doing high volume work require rapid and efficient cleaning procedures for cleaning paint equipment. Devices such as spray guns must be cleaned immediately after use in order to avoid drying of paint in the inner mechanism of the guns, as this leads to clogging of narrow channels and orifices therein. The chemicals generally employed in paint cleaning are highly volatile and flammable organic solvents which may present a health hazard upon direct exposure to either the liquid itself or the vapours thereof.
Presently available parts washers for cleaning paint spray guns and associated accessories are of several general types. One type utilizes a solvent pump for circulating paint removing solvent between a collection chamber and a washing chamber with the former situated substantially below the latter. There are two drawbacks to this type of arrangement. Firstly, the rate of solvent circulation is fixed by certain inherent properties of the pump including the internal dimensions of the fluid flow path through the pump and the speed of the solvent circulation means, usually a reciprocating piston. Secondly, since the solvent recirculation process involves drawing the solvent from the collection chamber through the pump and discharging it into the washing chamber, the pump intake in communication with the collection chamber is usually provided with a filter. This is necessary in order to prevent the intake of paint chips and other debris into the pump which would lead to clogging and loss of pumping efficiency over time. While the pump intake is usually positioned above the bottom of the collection chamber where the bulk of the paint debris collects, the pumping action of the pump will draw material into the filter thereby clogging the filter and hence slowing down the pumping rate over time. Accordingly there is a need to provide a parts washer with a solvent circulation system with greater pumping speeds and requiring minimal maintenance.
A second type of parts washer uses pressurized air to pressurize a solvent storage tank or holding tank, flowing the solvent under pressure to the washing chamber and using gravity to flow the paint saturated solvent back to the holding tank. Filters are arranged in the solvent return path for filtering out paint chips and other debris. Over time these filters must be removed and cleaned which can be a time consuming procedure. A difficulty with this type of parts washer is that it must be manually operated, and as such may, due to operator miscalculation, be run for too short a period of time resulting in the articles being improperly cleaned.
The build-up of solvent vapours within the washer during the cleaning procedure is circumvented in some cases by flowing compressed air through the working chamber following the solvent washing cycle. This serves to dry the cleaned parts in addition to reducing the build-up of vapours but is accomplished by manually opening an air valve after the washing cycle thereby necessitating the presence of an operator during the cleaning procedure.